A Brief (and Basic) Overview of Chromosome 16 Disorders
Every cell in the body should contain 23 pairs of chromosomes, which carry our hereditary material. Therefore, there should be two 16 chromosomes in each cell in the body. Sometimes, however, a chromosomal aberration can occur. Disorders associated with chromosome 16 abnormalities include:
A: Numerical Abnormalities
Full Trisomy 16: a chromosomal disorder in which an individual has three copies of chromosome 16 instead of the usual two. Trisomy 16 is not compatible with life and is the most common chromosomal cause of miscarriages (causing over 100,000 miscarriages annually in the U.S. alone).
Mosaic Trisomy 16: an extremely rare chromosomal disorder in which an extra chromosome 16 is present in some, but not all, of the cells of the affected individual's body. The affects of the disorder vary greatly, but some of the more common characteristics include intrauterine growth retardation (IUGR) and congenital heart defects.
Mosaic Trisomy 16 Confined to the Placenta (CPM): a condition in which the chromosome 16 abnormality is believed to be present only in the placental tissues.
Uniparental Disomy of Chromosome 16: a condition in which the chromosomes appear normal but both copies have originated from just one of the two parents (this is most often found in association with mosaic trisomy 16).
B: Structural Abnormalities
Every chromosome has two main parts, the short arm, called "p" for "petite", and the long arm, called "q." Individuals can have deletions or duplications of one of these arms, instead of the whole chromosome.
16p- (sixteen p minus): an extremely rare chromosomal disorder in which some portion in the short (p) arm of chromosome 16 is missing (deleted).
16q- (sixteen q minus): an extremely rare chromosomal disorder in which some portion of the long (q) arm of chromosome 16 is missing (deleted).
16p+ (sixteen p plus): an extremely rare chromosomal disorder in which some portion of the short (p) arm of chromosome 16 is duplicated.
16q+ (sixteen q plus): an extremely rare chromosomal disorder in which some portion of the long (q) arm of chromosome 16 is duplicated.
Unbalanced Translocation: a rare chromosomal disorder in which the deleted portion of a chromosome is attached to another chromosome.
Inversion: a rare chromosomal disorder in which a small portion of chromosome breaks off and then reinserts itself backwards.
There are many other combinations of deletions and/or duplications. This wide range of variation leads to a wide variety of outcomes, from no obvious problems to severe physical and mental handicaps. The more members we can add to the Foundation, the more information we can gather about common characteristics of chromosome 16 disorders.